In Kerbal Space Program, this corresponds to any anomaly that has been hidden in the game on the surfaces of bodies in the Kerbol System the Main Menu, in IVAs, and any other applicable area by the developers. This does not include bugs like terrain glitches.

This page contains spoilers, as you have already been warned. For any who wish to preserve the sense of exploration, please do not continue.

Celestial Bodies

Although originally a terrain glitch, the Mohole (a large, steep vertical "tunnel" at Moho's north pole) is often considered an Easter egg, and indeed was later "canonized" by the developers, being given its own biome (the "Northern Sinkhole") and KerbNet anomaly marker.

One Commnet station is called "Nye Island," named for science communicator Bill Nye.

I don't know if this would be considered an easter egg as such but apart from the eggs listed above and the official structures (KSC, Airfield runway, Woomerang launchpad, satellite stations, other) the are no actual kerbal towns, city's, or any other kind's of official habitations

The second space center, or "KSC2".

The crashed flying saucer.

The toilet found in the rubble of the Astronaut Complex

The smiley face on the seafloor can be seen faintly in the left half of this map, just south of the equator.

A camera mast based on that of the Curiosity rover can be found sticking out of a boulder. Originally it was embedded in the terrain itself before later being moved to the boulder, likely to prevent different terrain settings causing it to appear floating or underground. (30° 20′ 30″ S 28° 48′ 37″ W)

On the southern ice cap, there is a pyramidal hill that emits an SSTV signal. The source of the signal was several hundred meters beneath the hill as of 0.22, but as of 1.2, the signal is back at the surface. (66° 3′ 12″ S 160° 53′ 38″ W)

The Magic Boulder - Missing since 0.18 - The magic boulder used to orbit Ike at an altitude of 15 km with zero eccentricity and an inclination of 80 degrees. The mesh (physical surface) for the magic boulder did not match its texture (visible surface) which could result in ships apparently digging into the surface with no ill effect. It would also cause ships to explode seemingly spontaneously, sometimes metres away from the surface, displaying "vesselname crashed into Magic Boulder" in the Flight Log. It also seemed to glow green as if radioactive, and there was a Monolith on its leading edge. The boulder had no gravity, did not appear in the map view and could not be targeted, much like any other Easter egg, except in orbit. A successor to the magic boulder was later added.

Even though the "surface" of Jool is inaccessible (since it is a gas giant and parts are destroyed due to the pressure), there are still science logs for having landed on Jool: "You're not sure how you even landed on the surface of a gas giant. But it's probably best not to think about it for too long."

A Cave-like formation can be found at 40° 11′ 58″ N 174° 0′ 5″ E. Between 0.23 and 1.1.2 the cave was inadvertently placed hundreds of metres below the ground, but after 1.1.3 it has been fixed, and is once again on the surface.

Although since removed, there was once a crater with a faint image of Carl Sagan's face coloring the terrain.

Rarely, asteroids can be discovered with a texture featuring glowing cracks in a variety of colors, very similar to the original Magic Boulder orbiting Ike.

Easter Egg Narrative

In a forum post from late 2013,[1]Squad member Jeff C.(NovaSilisko) described an idea he had for connecting many easter eggs into a story concerning a civilization which predated the Kerbals. Experiments with interstellar travel resulted in the homeworld of this "precursor civilization" being flung out into an extremely distant orbit. Before they froze to death, they launched monoliths and other messages onto many planets and moons in hopes of seeding intelligent life. Instead, they created Kerbals, not-so-intelligent life.

The planet would not show up in any map and would be too distant to be observed with a telescope, making locating it by chance nearly impossible. However, players would be able to find transmitters beaming out SSTV signals on various bodies, each one of which would provide part of the orbital parameters necessary to locate it. The planet would be a bit smaller than Kerbin, covered in ruined cities and frozen oceans, and perpetually in twilight due to being so far from Kerbol.

The only element of this narrative which made it into the game is the SSTV transmitter on Duna, which transmits an image originally intended to depict 4 members of the precursor civilization standing on their homeworld, with the logo of their government. Had the narrative story been completed, it would also have contained part of the orbital parameters. Because the story was never implemented into the game, this explanation for the SSTV signal's imagery is arguably non-canon.[2]

Miscellaneous

The color of the Kerbals' skin is close to is #BADA55 () in hexadecimal but does not match it exactly. The hexadecimal RGB value spells like “badass” in leetspeak. Some say #84D455 () is the color of a Kerbal which is even further away than #BADA55. This connection is rumored, because Kerbals can have a BadS flag, which is usually interpreted as badass, and - when creating custom Kerbals - there are checkboxes for "Veteran" and "Badass".

An average of the skin color in Kerbal arm textures compared to the rumored colors

Some of the cockpits have post-it notes and other humorous writings inside them. The writing is somewhat blurry on normal settings and hard to read, but still legible. For transcripts of the notes, see the respective part pages.

When double-clicked on the screen which says "docking mode" in the mk1 cockpit, the IVA view changes to show upwards through the window on the top-back of the cockpit with a flight console. This suggests Kerbals can leave (or rotate?) their seats to make it easier to dock. It should be designed to be used with Inline Clamp-O-Tron.

The FL-T200 Fuel Tank has a very faint drawing on it which can just about be observed when fully zoomed in. The drawing becomes more visible during re-entry and appears to depict a failed re-entry procedure which has then been crossed out.

The Mk3 to Mk2 Adapter has the word "Kurvy" written on it, most likely a reference to its shape.

The EAS-4 Strut Connector has a cost of 42 an obvious reference to The Hitchhiker's guide to the galaxy's answer to the ultimate question.

The Telus Mobility Enhancer is similar to the ladder on the A-10 "Warthog" Close Ground Support Plane.

The LY series landing gear is a dual reference to Akron, Ohio based "Goodyear Tire & Rubber Company" and Buzz Lightyear from the Toy Story Franchise. On the tires,"Lightyear" is written.

The Kerbodyne Launch escape system has the designation A-004, a reference to A-004, the final test of the Apollo launch escape system

The Probodobodyne HECS says in the product description: "Despite concerns that one day, autonomous spacecraft cores could become self-aware and turn against their creators, or even become very stubborn against opening pod bay doors, Probodobodyne insists that these unmanned AI-driven devices are the way of the future." This is a reference to 2001: A Space Odyssey, in which the self-aware computer system HAL-9000 becomes very rebellious and eventually refuses to open the pod bay doors for the human astronaut Dave Bowman.

A comparison between the ladder in-game and the ladder on the A-10.

The PB-NUK radioscope thermoelectric generator discription says ‘not to be used a heating during emergency rover exursions’

This is a reference to The Martian, a book and movie where the main character, Mark Whattney uses a similar generater as a heat scource when he drives across the surface of mars.

One of the loading hints is "Falling With Style...", which may be a reference to Toy Story when Woody says, "That's not flying, that's falling with style!"

Main Menu

One of the two main menu images is that of a Kerbal standing on the Mun's surface, with Kerbin in the background. There is a 1 in 40 chance that a sand castle made of Mun dust can be seen near his feet.

The Mun dust castle.

Other

On the website "Kerbal Maps" - which shows maps of all the planetary bodies in the game - the URL contains the word "finitemonkeys", this being a reference to "The Infinite Monkey Theorum".

Scenarios

During the Space Station One scenario, by zooming out far enough to show the planetary map, a ship by the name of 'Kerbal XX' can be seen orbiting around Duna in a near-equatorial orbit (as of 0.23)

Kerbal XX from the Station 1 scenario.

Patcher

If you look into the patcher log, before updating, the log says "HOLD ON TO YOUR BUTTS!"